INSECTs AND OTHER ANIMAL Pests LnyurRioUs To FIELD BEANS 1023 
on which only a dark green spot on the lighter green of the pod gave 
evidence of the deformation within. 
Other insects that produce pits in beans are the spined tobacco bug 
(Huschistus variolarius, Plate LX XI, 1), of the family Pentatomidae, and 
the tarnished plant bug (Lygus pratensis). Specimens of Huschistus 
variolarius placed with beans on August 19 had produced small pits on 
them by September 8. Nymphs and adults of Lygus pratensis left with a 
plant for nineteen days also produced small dimples. Similar work of this 
insect was reported from Michigan some years ago. During late summer 
both these insects, together with the apple leaf hopper (Hmpoasca mali), 
have been found in the field with their beaks inserted in the pods. Cage 
experiments seem to show, however, that the beak of the leaf hopper is too 
short to penetrate the pod and injure the beans within. In the summer of 
1920, these experiments were repeated and the injuries from the insects 
were of the same kind as had been caused by them the preceding year. 
The extent of the damage caused by these pests is not great, but each 
year there are a few beans of this kind in the product of almost all fields 
and gardens. Injury is especially noticeable in places where ragweed and 
lamb’s-quarters are allowed to grow. The most disfigured of the field 
beans are discarded, with the diseased and immature seed, when they are 
picked and graded in the warehouse. 
THE ROLE OF INSECTS IN THE TRANSMISSION OF BEAN DISEASES 
Bean diseases frequently spread thru a field with great rapidity, and it 
sometimes appears as tho this spread might be due to, or at least hastened 
by, the presence of insects. In cooperation with Dr. W. H. Burkholder, 
of the Department of Plant Pathology at Cornell University, experiments 
were conducted in the summer of 1918 in an effort to determine what insects 
were instrumental in the spread of the bacterial blight of beans (caused by 
Bacterium phaseoli E. F. Smith). 
On August 22, 1918, eight specimens of each of the commoner insects 
on bean foliage, including the red-headed flea beetle (Systena frontalis), 
the dusky plant bug (Adelphocorus rapidus), the apple leaf hopper 
(Empoasca mali), and the nine-spotted lady bug (Coccinella novemnolata), 
were rubbed ‘n a virulent culture of the blight organism or allowed to 
crawl for an hour on bean leaves smeared with the culture. The insects 
were then placed in separate field cages (fig. 100, D, page 1016) on varieties 
of beans free from blight but susceptible to it. As a check, insects of the 
same species, collected in the same field but not treated with the pathogene, 
were placed in similar cages. Blight did not develop in any of the cages. 
In 1919 the same species of insects that were used in 1918, and in addition 
the tarnished plant bug (Lygus pratensis), were used in the experiments. 
The insects were taken from a severely blighted field of red kidney beans, 
and after being caged for some time with these diseased plants they were 
